Hedges as contemplated for trimming with the present tool, typically consist of stem diameters ranging from the very slim or fine stems to stems having diameters approaching three-quarters of an inch. A trimmer having double acting blades has a scissors-like action whereby a pair of cutting blades have laterally projected sharpened teeth providing cutting edges that move back and forth in opposite directions. The opposing reciprocation of the cutting teeth causes the teeth to first move apart to create an opening between the teeth in which the hedge materials enter and then they move together to sever those materials. Hereafter the opening between the cutting teeth are referred to as cutting chambers.
There are a number of the features that are common to a double acting hedge trimmer. The cutting chamber has an opening that allows entry of materials. A hood shape is provided at the entry to the cutting chamber to grab and draw the hedge material into the opening. A guard portion extends outwardly of the cutting teeth of one of the blades, i.e., the guard portion protrudes beyond the cutting edge. The adjacent guard portions in response to an established safety regulation, cooperate to prevent entry of a circular stem having a three-quarter inch diameter. That is, no portion of the three-quarter inch stem is allowed to enter the cutting chamber. Thus, the guard portions are configured to have inwardly directed abutments spaced outwardly from the cutting chamber entry and forming a gate or throat through which the hedge materials must pass in order to enter the cutting chamber. A three-quarter inch diameter stem will engage the abutments and thereby be prevented from entering the cutting chamber, i.e., the reciprocating cutting edges will not cut into the stem.
The above requirement of the guard portion generates several problems. The guard portion's outer tip cannot be allowed to have a broad edge that engages the hedge material. If the tip is broad, the hedge material is simply pushed away from and under the blade assembly and doesn't get cut. Thus, the guard portion is formed like an arrowhead, with the base of the head defined by the hook shaped entry into the cutting chamber, and with the sides angled inwardly first to the point of abutment (where the three-quarter inch stem is rejected) and then to a narrow. Whereas the safety regulation, hook shaped grabbing, and narrow tip features are satisfied, the resulting angled sides of the guard portion act as camming surfaces to cam the stems away from rather than into the cutting chamber.